The disclosure: a positive mirror FET, through which a positive mirror current that is proportional to a positive-direction current in currents of an output FET in positive and negative directions is made to flow; a first operational amplifier, receiving a constant voltage at one end, receiving an upstream side voltage regarding the positive mirror current of the positive mirror FET at the other end, and outputting a voltage corresponding to the upstream side voltage regarding the positive mirror current of the positive mirror FET by converting an output voltage into a current and feeding back the current to the other end; a negative mirror FET, through which a negative mirror current that is proportional to a negative-direction current in the currents of the output FET in positive and negative directions is made to flow; and a second operational amplifier, receiving a constant voltage at one end, receiving an upstream side voltage regarding the negative mirror current of the negative mirror FET at the other end, and outputting a voltage corresponding to the upstream side voltage regarding the negative mirror current of the negative mirror FET by converting an output voltage into a current and feeding back the current to the other end. A detection value is output based on an output current obtained by adding a positive output current corresponding to the output of the first operational amplifier and a negative output current corresponding to the output of the second operational amplifier.